Dual-Polarized L-Band SAR Imagery for Temporal Monitoring of Marine Oil Slick Concentration

Sébastien Angelliaume,Olivier Boisot,Charles-Antoine Guérin

doi:10.3390/rs10071012

Abstract

SAR sensors are usually used in the offshore domain to detect marine oil slicks which allows the authorities to guide cleanup operations or prosecute polluters. As radar imagery can be used any time of day or year and in almost any weather conditions, the use and programming of such remote sensing data is usually favored over optical imagery. Nevertheless, images collected in the optical domain provide access to key information not accessible today by SAR instruments, such as the thickness or the amount of pollutant. To address this knowledge gap, a methodology based on the joint use of a scattering model (U-WCA) and remote sensing data collected by a low frequency (e.g., L-band) imaging radar over controlled release of mineral oil spill is reported in this paper. The proposed method allows estimation of the concentration of pollutant within an oil-in-water mixture as well as the temporal variation of this quantity due to weathering processes.

Highlights

The authorities and petroleum companies usually use airborne and spaceborne SAR (Synthetic Aperture Radar) images to detect and monitor marine slicks [1,2]
A methodology to estimate the proportion of oil within an oil-in-water marine slick mixture has been reported in this paper as well as its application to the temporal monitoring of the oil concentration
The key aspects of this study rely on three elements: the use of a rigorous surface scattering model to estimate the polarization ratio; the estimation of the volume fraction of oil from the Bruggemann formula; and the uniqueness of the dataset collected from controlled releases of mineral oil by an airborne SAR sensor operating at L-band, characterized by an instrument noise floor that is much lower than is currently available from spaceborne SARs

Summary

Introduction

The authorities and petroleum companies usually use airborne and spaceborne SAR (Synthetic Aperture Radar) images to detect and monitor marine slicks [1,2]. This deviation as well as the use of images collected with insufficient Signal to Noise Ratio (SNR) over slick-covered sea surface [7], is a major issue when trying to derive the surface properties of marine slick from remote sensing SAR data It has been previously reported in [12,20] that for radar operating at low EM frequency (e.g., L-band) the relative contribution of the non-polarized component with respect to the total power scattered from the ocean surface is negligible.

Bragg Scattering Theory

Impact of Oil on the Sea Surface

Airborne SAR Acquisitions

The Universal Weighted Curvature Approximation Scattering Model

Findings

Conclusions